KR20140119255A - Manufacturing method of forming thin film solar cell, and thin film solar cell formed by the method - Google Patents

Abstract

Preparing a reaction solution having an ammonia compound, a zinc source, and a sulfur source at a temperature lower than 70 캜; And a substrate on which a light absorption layer is formed in the reaction solution, wherein the zinc source has a concentration of 0.01M to 0.09M, and a thin film solar cell formed by the method .

Description

[0001] The present invention relates to a method of forming a thin film solar cell and a thin film solar cell formed by the method,

More particularly, the present invention relates to a manufacturing method of forming a buffer layer for a thin film solar cell, and a manufacturing method of the thin film solar cell including the buffer layer formed by the manufacturing method Battery.

With the recent depletion of existing energy sources such as oil and coal, interest in alternative energy to replace them is increasing. Among them, solar cells are attracting attention as a next-generation battery that converts solar energy directly into electrical energy using semiconductor devices.

The most basic structure of a solar cell is a diode type composed of a pn junction, which is classified according to the material of the light absorbing layer.

A solar cell using silicon as a light absorbing layer can be classified into a crystalline (monocrystalline, polycrystalline) wafer type solar cell and a thin film (amorphous, polycrystalline) solar cell. (CIGS type) compound or CdTe compound which is substituted with S or not with S as the light absorption layer, a thin film type solar cell, a III-V type solar cell, a dye-sensitized solar cell, A solar cell is a typical solar cell.

       In the CIGS thin film solar cell, a CdS buffer layer or a Cd-free buffer layer in which Cd, which is a harmful component to human body, may be used as a buffer layer, and a Cd-free buffer layer is formed by a chemical bath deposition (CBD) .

       Such a chemical solution growth method is currently widely used as a method of cleaning impurities on the surface of a light absorbing layer and then substituting and etching a zinc source in a vacancy region near the surface of the light absorbing layer. The formed buffer layer may vary depending on the composition, but it may have a thickness of 50 nm or less.

 However, such a Cd-free buffer layer is problematic in terms of cost and environment in that it takes a longer time to form a film than the CdS buffer layer and the reaction solution can not be used continuously and it needs to be replaced with a new solution.

      Therefore, there is still a need for a method of forming a thin film solar cell ensuring time-consuming use of the reaction solution and a thin film solar cell maintaining excellent electrical characteristics for a long time.

One aspect is to provide a manufacturing method for forming a thin film solar cell ensuring time for allowing a reaction solution to be continuously used.

Another aspect is to provide a thin film solar cell in which excellent electrical characteristics are maintained for a long time.

According to one aspect,

Preparing a reaction solution having an ammonia compound, a zinc source, and a sulfur source at a temperature lower than 70 캜; And

And a substrate on which a light absorption layer is formed in the reaction solution, wherein the concentration of the zinc source is 0.01M to 0.09M.

The step of preparing the reaction solution may be a step of preparing a reaction solution at 60 ° C to 70 ° C.

The preparing of the reaction solution may include preparing a solution containing the sulfur source and a mixed solution containing the ammonia compound and the zinc source separately, and then mixing the solutions.

The step of preparing the sulfur source may include a step of stirring the sulfur source in DI water at a temperature of 70 ° C to 90 ° C.

The step of preparing the mixed solution in which the ammonia compound and the zinc source are mixed may include a step of mixing the ammonia compound and the zinc source at room temperature.

The concentration of the ammonia compound may be 1.0M to 5.0M.

The concentration of the sulfur source may be between 0.1M and 0.7M.

The manufacturing method may further include a step of cleaning after the step of supporting the substrate on which the light absorption layer is formed in the reaction solution.

The manufacturing method may further include a step of drying after the cleaning step.

The light transmittance of the reaction solution may be 60% or more from the time of the reaction of the solution until 4 hours.

According to another aspect,

Board;

A rear electrode layer formed on the substrate;

A light absorbing layer formed on the rear electrode layer;

A buffer layer formed on the light absorbing layer by the above-described manufacturing method; And

And a transparent electrode layer formed on the buffer layer.

According to an aspect of the present invention, there is provided a process for preparing a reaction solution in which the concentration and temperature of a zinc source are adjusted to form a thin film solar cell having a sufficient time for allowing the reaction solution to be continuously used. Thin film solar cells can maintain excellent electrical properties for a long time.

1 is a flowchart of a manufacturing method for forming a buffer layer for a thin film solar cell according to an embodiment.
FIG. 2 is a process flow diagram of a step of preparing a reaction solution in a manufacturing method for forming a buffer layer for another thin film solar cell in one embodiment.
3 is a schematic diagram showing a thin film solar cell according to one embodiment.
4 is a graph showing changes in light transmittance with time for the reaction solution used in the buffer layer of the thin film solar cell manufactured in Examples 1 to 4 and Comparative Examples 1 to 4.

Hereinafter, a method of forming a thin film solar cell according to an embodiment of the present invention and a thin film solar cell formed by the method will be described in detail. The present invention is not limited thereto, and the present invention is only defined by the scope of the following claims.

In the following drawings, each component is exaggerated, omitted, or schematically shown for convenience and clarity of explanation, and the size of each component does not entirely reflect the actual size. Also, in the description of each element, in the case of being described as being formed on "on," " on "means that it is formed directly or through other elements The reference to "on" will be described with reference to the drawings. In addition, in the description of each component, when it is described as being formed "upper" or "lower" Quot; upper "or " lower" refers to being formed indirectly through another component, and reference to "upper & Will be described with reference to the drawings.

1 is a flowchart of a manufacturing method for forming a buffer layer for a thin film solar cell according to an embodiment.

Referring to FIG. 1, in one aspect, a method of forming a buffer layer for a thin film solar cell comprises: preparing a reaction solution containing an ammonia compound, a zinc source, and a sulfur source; And a substrate having a light absorption layer formed on the reaction solution, wherein the concentration of the zinc source may be 0.01M to 0.09M.

For example, the step of preparing the reaction solution may be a step of preparing a reaction solution at 60 ° C to 70 ° C.

Generally, a method of forming a buffer layer for a thin film solar cell uses a reaction solution at 70 ° C to 95 ° C. However, in the reaction solution at such a high temperature as described above, the reaction speed of the solution is rapid, so that colloid can be formed rapidly in the solution. Such a colloid is attached to the surface of the light absorbing layer repeatedly, causing a problem in the shunt path . As a result, the reaction solution can not be continuously used for a long time, and the solution must be replaced with a new solution, which is costly and environmentally problematic.

The thin film solar cell buffer layer may be prepared by preparing a reaction solution having a temperature of less than 70 ° C., for example, at 60 ° C. to 70 ° C., containing the ammonia compound, a zinc source, and a sulfur source, By keeping the light transmittance of about 60% or more from the beginning of the reaction, the reaction rate can be constantly controlled for a long time. Therefore, the thin film solar cell including the buffer layer manufactured by the method of forming the buffer layer for the thin film solar cell can maintain excellent electrical characteristics for a long time.

FIG. 2 is a process flow diagram of a step of preparing a reaction solution in a manufacturing method for forming a buffer layer for another thin film solar cell in one embodiment.

Referring to FIG. 2, the preparing of the reaction solution may include preparing a mixed solution containing the sulfur source and the ammonia compound and a zinc source separately, and then mixing the solutions.

The step of preparing the sulfur source may include a step of stirring the sulfur source in DI water at a temperature of 70 ° C to 90 ° C.

The step of preparing the mixed solution in which the ammonia compound and the zinc source are mixed may include a step of mixing the ammonia compound and the zinc source at room temperature.

Preparing the reaction solution by preparing the sulfur source at a temperature higher by about 10 ° C to 20 ° C than the temperature of the reaction solution and mixing the mixed solution of the ammonia compound and the zinc source mixed at room temperature into the prepared sulfur source solution The reaction rate can be constantly controlled for a long time by adjusting the temperature to less than 70 ° C from the beginning.

Further, when the temperature of the ammonia compound and the zinc source is increased, the concentration of the ammonia compound is changed according to the volatilization of the ammonia compound, so that the mixture is mixed at room temperature to form a bond between the Zn ²⁺ and the ammonia compound So that ZnO formation can be appropriately controlled.

The ammonia compound may include an aqueous ammonia solution (NH ₄ OH) or the like.

The concentration of the ammonia compound may be 1.0M to 5.0M. Cu _x Se or Cu-rich site on a (Cu rich site) [Cu ( NH 4) 3] 2+ or _{[Cu (NH 4) 2]} 2+ , which ammonia compound having a concentration within the above range are present in the light absorbing layer and the surface By removing the same copper ammonia complexes, it is possible to control the shunt path and the characteristics of band alignment can be improved. The ammonia compound binds with Zn ²⁺ of the zinc source to form a ligand to induce binding of zinc to the surface of the light absorbing layer and to control the rate at which the buffer layer is formed on the surface of the light absorbing layer.

The zinc source may comprise a zinc salt or a zinc compound. For example, the zinc source is _{ZnSO 4, ZnCl 2, Zn 2} (CH 3 COO), Zn (NO 3) 2, And a hydrate of these compounds. The zinc source is displaced and diffused into the surface of the light absorbing layer to allow the growth of the buffer layer to progress.

The concentration of the zinc source may be, for example, 0.01 M to 0.07 M, for example.

When the concentration of the zinc source is increased to a concentration within the above range, the thickness of the buffer layer for a thin film solar cell can be increased while minimizing the light transmittance. Specifically, even if the concentration of the zinc source in the reaction solution of less than 70 캜 is rapidly increased to the concentration within the above range, the light transmittance can be maintained at 70% for 1 hour, and the time for 1 hour to 1 hour 30 minutes The change of transmittance is generated, but after 1 hour and 30 minutes, the change of light transmittance is minimized and the reaction can proceed.

The oxysulfide may include a thiourea-based compound. The oxides allow a uniform buffer layer to be formed on the light absorption layer. The concentration of the sulfur source may be between 0.1M and 0.7M.

The manufacturing method may further include a step of cleaning after the step of supporting the substrate on which the light absorption layer is formed in the reaction solution. The step of cleaning may include a step of first cleaning with an alkali solution of 5% by weight or less at 50 ° C, followed by a secondary cleaning with DI water. The alkali solution may be an ammonia compound.

For example, in the case of a high concentration zinc source of 0.1 M, if it is cleaned only with DI water, the surface of the light absorbing layer and the ammonia compound and sulfur source contained in the reaction solution undergo rapid pH change Can easily occur due to the reaction with oxygen, and the composition and thickness of the buffer layer can be made non-uniform. Therefore, the electrical characteristics of the thin film solar cell including such a buffer layer may be deteriorated. Therefore, it is preferable to further include a step of firstly cleaning the substrate with an alkali solution of 5% by weight or less at 50 ° C before the step of secondly cleaning with DI water, thereby preventing the formation of a stain on the buffer layer, Can be improved.

The manufacturing method may further include a step of drying after the cleaning step. The drying step may include a step of drying under an atmosphere of an inert gas. The inert gas may include N ₂ gas or the like.

In the above manufacturing method, a buffer layer of ZnS, ZnO, or ZnS (O, OH) can be formed on the substrate having the light absorption layer formed thereon. Unlike CdS, this buffer layer contains no harmful Cd, which is advantageous in terms of environment and can form a thin layer. The thickness of the buffer layer may be 10 nm to 50 nm.

The reaction solution can be used up to 6 hours. For example, the light transmittance of the reaction solution may be 60% or more by 4 hours. By keeping the light transmittance of the reaction solution above 60% until 4 hours, the reaction rate of the solution can be kept constant and the reaction solution can be used continuously for a long time.

In another aspect, A rear electrode layer formed on the substrate; A light absorbing layer formed on the rear electrode layer; A buffer layer formed on the light absorbing layer by the above-described manufacturing method; And a transparent electrode layer formed on the buffer layer.

3 is a schematic diagram showing a thin film solar cell according to one embodiment.

3, a substrate 100, a rear electrode layer 200 formed on the substrate 100, a light absorbing layer 300 formed on the rear electrode layer 200, a buffer layer 400 formed on the light absorbing layer 300, And a transparent electrode layer 500 formed on the buffer layer 400.

First, the substrate 100 may be formed of glass or polymer substrate having excellent light transmittance. For example, sodalime glass or high strained point soda glass may be used as the glass substrate, and polyimide may be used as the polymer substrate. However, Do not. Further, the glass substrate can be formed of a low-iron-content tempered glass containing a small amount of iron in order to protect internal elements from an external impact or the like and to increase the transmittance of sunlight. In particular, the low iron soda lime glass can further improve the efficiency of the light absorption layer 300 by dissolving Na ions in the glass at a process temperature exceeding 500 캜.

The rear electrode layer 200 may be formed of a metal such as molybdenum (Mo), aluminum (Al), or the like so as to collect the charge formed by the photoelectric effect, reflect the light transmitted through the light absorption layer 300, ) Or copper (Cu), and the like. In particular, the back electrode layer 200 may be formed of Mo including Mo, taking into account high conductivity, ohmic contact with the light absorption layer 300, and high temperature stability under selenium (Se) atmosphere.

The back electrode layer 200 may be formed by applying a conductive paste on the substrate 100 and then performing a heat treatment, or may be formed through a process such as plating. Further, it can be formed by a sputtering process using, for example, a molybdenum (Mo) target.

The rear electrode layer 200 may have a thickness of 200 to 500 nm and may be divided into a plurality of portions by, for example, a first separation groove (not shown). The first separation groove may be a groove formed in a direction parallel to one direction of the substrate 100.

The first isolation groove is formed by forming a rear electrode layer 200 on the substrate 100 and then dividing the rear electrode layer 200 into a plurality of portions by performing first patterning. The first patterning may be performed, for example, by a laser scribing process. The laser scribing process is a process of evaporating a part of the rear electrode layer 200 by irradiating a laser from the bottom of the substrate 100 toward the substrate 100. Thereby, the rear electrode layers 200 are separated from each other A first separation groove may be formed so as to divide it into a plurality of parts.

On the other hand, the rear electrode layer 200 may be doped with an alkali ion such as Na. For example, when the light absorbing layer 300 is grown, the alkali ion doped in the rear electrode layer 200 is mixed with the light absorbing layer 300 to have a favorable structural effect on the light absorbing layer 300, The conductivity can be improved. Accordingly, the open-circuit voltage V _oc of the solar cell 600 increases, and the efficiency of the solar cell 600 can be improved.

In addition, the rear electrode layer 200 may be formed of a multilayer film for bonding with the substrate 100 and securing the resistance characteristics of the rear electrode layer 200 itself.

The light absorption layer 300, a Cu (In, Ga) is substituted by S (Se, S) ₂ compounds, or that are not substituted by S Cu (In, Ga) Se ₂ compound copper-indium-gallium-selenide-based ( CIGS) compound to form a P-type semiconductor layer, and absorb incident solar light. The light absorption layer 300 may be formed to have a thickness of 0.7 to 2 탆 and may be formed in a separation groove for dividing the rear electrode layer 200.

The light absorption layer 300 is formed by co-depositing copper (Cu), indium (In), gallium (Ga), selenium (Se) or the like into a small electric furnace provided in a vacuum chamber, evaporation) method, a copper (Cu) target, an indium (in) target, gallium (Ga) was formed by using the target, the back electrode layer (200), CIG based metal peurikeo prelude (precusor on) film, and hydrogen selenide (H ₂ Se can be formed by a sputtering / selenization method in which the metal precursor film reacts with selenium (Se) to form the light absorbing layer 300 by heat treatment in a gas atmosphere. Also, the light absorption layer 300 can be formed by an electro-deposition method, a molecular organic chemical vapor deposition (MOCVD) method, or the like.

The buffer layer 400 reduces the band gap difference between the P type light absorbing layer 300 and the N type light transmitting electrode layer 500 and the recombination of electrons and holes that may occur between the light absorbing layer 300 and the light transmitting electrode layer 500 , And can be formed by chemical bath deposition (CBD) as described above.

Meanwhile, the light absorption layer 300 and the buffer layer 400 may be separated into a plurality of portions by a second separation groove (not shown). The second separation groove may be a groove formed in parallel with the first separation groove at a position different from the first separation groove and the upper surface of the lower electrode layer 200 is exposed by the second separation groove.

After the light absorption layer 300 and the buffer layer 400 are formed, the second patterning is performed to form a second separation groove (not shown). The second patterning may be performed, for example, by mechanical scribing which forms a second separation groove by moving a sharp tool such as a needle in a direction parallel to the first separation groove at a position spaced apart from the first separation groove scribing. However, the present invention is not limited thereto, and a laser may be used.

The second patterning divides the light absorbing layer 300 into a plurality of portions and the second isolation groove formed by the second patterning extends to the upper surface of the rear electrode layer 200 to expose the rear electrode layer 200.

The light transmitting electrode layer 500 forms a P-N junction with the light absorbing layer 300. Further, the light transmitting electrode layer 500 is made of a transparent conductive material such as ZnO: B, AZO, ITO, or IZO, and captures a charge formed by the photoelectric effect. The light transmitting electrode layer 500 may be formed by a metalorganic chemical vapor deposition (MOCVD) method, a low pressure chemical vapor deposition (LPCVD) method, a sputtering method, or the like.

Although not shown in the drawings, the upper surface of the transparent electrode layer 500 can be textured in order to reduce reflection of incident sunlight and increase light absorption into the light absorption layer 300.

The light-transmitting electrode layer 500 is formed in the second isolation groove and contacts the lower electrode layer 200 exposed by the second isolation groove to form a plurality of light-absorbing layers 300 ) Are electrically connected.

The light transmitting electrode layer 500 may be divided into a plurality of portions by a third separation groove (not shown) formed at a position different from the first separation groove and the second separation groove. The third separation groove may be a groove formed parallel to the first separation groove and the second separation groove and may extend to the upper surface of the rear electrode layer 200. At this time, the third separation groove may be filled with an insulating material such as air.

And the third separation groove is formed by performing the third patterning. The third patterning can be performed by mechanical scribing and the third isolation groove formed by the third patterning extends to the top surface of the rear electrode layer 200 to form a plurality of photoelectric conversion units. Also, the third isolation groove may be filled with air or the like to form an insulating layer.

Although not shown in the drawing, the upper surface of the transparent electrode layer 500 may have a textured surface. Texturing means forming a concave-convex pattern on the surface by a physical or chemical method. When the surface of the transparent electrode layer 500 is roughly textured, the reflectance of the incident light is reduced The light trapping amount can be increased. Therefore, an effect of reducing the optical loss can be obtained.

Hereinafter, examples and comparative examples of the present invention will be described. However, the following examples are only illustrative of the present invention, and the present invention is not limited to the following examples.

[Example]

(Preparation of Thin Film Solar Cell)

Example 1

A soda lime glass substrate having a thickness of about 1 mm and having a Mo back electrode layer coated thereon was prepared. A CuGa target and an In target were sputtered on the substrate coated with the Mo back electrode layer, respectively, and heat-treated at 400 ° C for 20 minutes and at 550 ° C for 60 minutes under H ₂ Se and H ₂ S atmospheres, respectively, to obtain a composition of CuIn _0.7 Ga _0.3 SSe ₂ Was formed.

A buffer layer was formed on the light absorption layer using a chemical solution deposition method (Chemical Bath Deposition: CBD) as follows.

First, a solution of SC (NH ₂ ) ₂ was prepared by stirring DI water and 0.55M SC (NH ₂ ) ₂ at a temperature of about 77.5 ± 2.5 ° C. Separately, NH ₄ OH 2.5M, and a mixture of ZnSO _{4 ·} 7H ₂ O 0.025M at room temperature to prepare a mixed solution of NH ₄ OH and ZnSO _{4 ·} 7H ₂ O. The SC (NH ₂ ) ₂ solution and the mixed solution of NH ₄ OH and ZnSO ₄ .7H ₂ O were put into the reactor and mixed to prepare a reaction solution at 62.5 ± 2.5 ° C.

The substrate on which the light absorbing layer was formed was carried in the reaction solution for 10 minutes. The substrate was washed with DI water and dried under N ₂ gas for 5 minutes to form a 0.5 nm thick buffer layer for a thin film solar cell on the light absorption layer.

A ZnO light-transmitting electrode layer was formed on the buffer layer by metalorganic chemical vapor deposition (MOCVD) to produce a thin film solar cell.

Example 2

A soda lime glass substrate having a thickness of about 1 mm and having a Mo back electrode layer coated thereon was prepared. A CuGa target and an In target were sputtered on the substrate coated with the Mo back electrode layer, respectively, and heat-treated at 400 ° C for 20 minutes and at 550 ° C for 60 minutes under H ₂ Se and H ₂ S atmospheres, respectively, to obtain a composition of CuIn _0.7 Ga _0.3 SSe ₂ Was formed.

A buffer layer was formed on the light absorption layer using a chemical solution deposition method (Chemical Bath Deposition: CBD) as follows.

First, SC (NH ₂ ) ₂ solution was prepared by stirring DI water and 0.55M SC (NH ₂ ) ₂ at a temperature of about 82.5 ± 2.5 ° C. Separately, NH ₄ OH 2.5M, and a mixture of ZnSO _{4 ·} 7H ₂ O 0.025M at room temperature to prepare a mixed solution of NH ₄ OH and ZnSO _{4 ·} 7H ₂ O. The SC (NH ₂ ) ₂ solution and a mixed solution of NH ₄ OH and ZnSO _{4 ·} 7H ₂ O were charged into the reactor and mixed to prepare a reaction solution at 67.5 ± 2.5 ° C.

The substrate on which the light absorbing layer was formed was carried in the reaction solution for 10 minutes. The substrate was washed with DI water and dried under N ₂ gas for 5 minutes to form a 0.5 nm thick buffer layer for a thin film solar cell on the light absorption layer.

A ZnO light-transmitting electrode layer was formed on the buffer layer by metalorganic chemical vapor deposition (MOCVD) to produce a thin film solar cell.

Example 3

A soda lime glass substrate having a thickness of about 1 mm and having a Mo back electrode layer coated thereon was prepared. A CuGa target and an In target were sputtered on the substrate coated with the Mo back electrode layer, respectively, and heat-treated at 400 ° C for 20 minutes and at 550 ° C for 60 minutes under H ₂ Se and H ₂ S atmospheres, respectively, to obtain a composition of CuIn _0.7 Ga _0.3 SSe ₂ Was formed.

A buffer layer was formed on the light absorption layer using a chemical solution deposition method (Chemical Bath Deposition: CBD) as follows.

First, a solution of SC (NH ₂ ) ₂ was prepared by stirring DI water and 0.55M SC (NH ₂ ) ₂ at a temperature of about 77.5 ± 2.5 ° C. Separately, NH ₄ OH 2.5M, and a mixture of ZnSO _{4 ·} 7H ₂ O 0.055M at room temperature to prepare a mixed solution of NH ₄ OH and ZnSO _{4 ·} 7H ₂ O. The SC (NH ₂ ) ₂ solution and the mixed solution of NH ₄ OH and ZnSO ₄ .7H ₂ O were put into the reactor and mixed to prepare a reaction solution at 62.5 ± 2.5 ° C.

The substrate on which the light absorbing layer was formed was carried in the reaction solution for 10 minutes. The substrate was washed with DI water and dried under N ₂ gas for 5 minutes to form a 0.5 nm thick buffer layer for a thin film solar cell on the light absorption layer.

A ZnO light-transmitting electrode layer was formed on the buffer layer by metalorganic chemical vapor deposition (MOCVD) to produce a thin film solar cell.

Example 4

A soda lime glass substrate having a thickness of about 1 mm and having a Mo back electrode layer coated thereon was prepared. A CuGa target and an In target were sputtered on the substrate coated with the Mo back electrode layer, respectively, and heat-treated at 400 ° C for 20 minutes and at 550 ° C for 60 minutes under H ₂ Se and H ₂ S atmospheres, respectively, to obtain a composition of CuIn _0.7 Ga _0.3 SSe ₂ Was formed.

A buffer layer was formed on the light absorption layer using a chemical solution deposition method (Chemical Bath Deposition: CBD) as follows.

First, a solution of SC (NH ₂ ) ₂ was prepared by stirring DI water and 0.55M SC (NH ₂ ) ₂ at a temperature of about 77.5 ± 2.5 ° C. Separately, NH ₄ OH 2.5M, and a mixture of ZnSO _{4 ·} 7H ₂ O 0.085M at room temperature to prepare a mixed solution of NH ₄ OH and ZnSO _{4 ·} 7H ₂ O. The SC (NH ₂ ) ₂ solution and the mixed solution of NH ₄ OH and ZnSO ₄ .7H ₂ O were put into the reactor and mixed to prepare a reaction solution at 62.5 ± 2.5 ° C.

The substrate on which the light absorbing layer was formed was carried in the reaction solution for 10 minutes. The substrate was washed with DI water and dried under N ₂ gas for 5 minutes to form a 0.5 nm thick buffer layer for a thin film solar cell on the light absorption layer.

A ZnO light-transmitting electrode layer was formed on the buffer layer by metalorganic chemical vapor deposition (MOCVD) to produce a thin film solar cell.

Comparative Example 1

A soda lime glass substrate having a thickness of about 1 mm and having a Mo back electrode layer coated thereon was prepared. A CuGa target and an In target were sputtered on the substrate coated with the Mo back electrode layer, respectively, and heat-treated at 400 ° C for 20 minutes and at 550 ° C for 60 minutes under H ₂ Se and H ₂ S atmospheres, respectively, to obtain a composition of CuIn _0.7 Ga _0.3 SSe ₂ Was formed.

A buffer layer was formed on the light absorption layer using a chemical solution deposition method (Chemical Bath Deposition: CBD) as follows.

First, SC (NH ₂ ) ₂ solution was prepared by stirring DI water and 0.55M SC (NH ₂ ) ₂ at a temperature of about 82.5 ± 2.5 ° C. Separately, NH ₄ OH 2.5M, and a mixture of ZnSO _{4 ·} 7H ₂ O 0.025M at room temperature to prepare a mixed solution of NH ₄ OH and ZnSO _{4 ·} 7H ₂ O. The SC (NH ₂ ) ₂ solution and a mixed solution of NH ₄ OH and ZnSO _{4 ·} 7H ₂ O were put into the reactor and mixed to prepare a reaction solution at 72.5 ± 2.5 ° C.

The substrate on which the light absorbing layer was formed was carried in the reaction solution for 10 minutes. The substrate was first washed with 5 wt% NH ₄ OH to form a buffer layer for a thin film solar cell with a thickness of 0.5 nm on the light absorption layer.

A ZnO light-transmitting electrode layer was formed on the buffer layer by metalorganic chemical vapor deposition (MOCVD) to produce a thin film solar cell.

Comparative Example 2

A soda lime glass substrate having a thickness of about 1 mm and having a Mo back electrode layer coated thereon was prepared. A CuGa target and an In target were sputtered on the substrate coated with the Mo back electrode layer, respectively, and heat-treated at 400 ° C for 20 minutes and at 550 ° C for 60 minutes under H ₂ Se and H ₂ S atmospheres, respectively, to obtain a composition of CuIn _0.7 Ga _0.3 SSe ₂ Was formed.

A buffer layer was formed on the light absorption layer using a chemical solution deposition method (Chemical Bath Deposition: CBD) as follows.

First, a solution of SC (NH ₂ ) ₂ was prepared by stirring DI water and 0.55M SC (NH ₂ ) ₂ at a temperature of about 77.5 ± 2.5 ° C. Separately, a mixed solution of NH ₄ OH and ZnSO ₄ .7H ₂ O was prepared by mixing 2.5M of NH ₄ OH and 0.1M of ZnSO ₄ .7H ₂ O at room temperature. The SC (NH ₂ ) ₂ solution and the mixed solution of NH ₄ OH and ZnSO ₄ .7H ₂ O were put into the reactor and mixed to prepare a reaction solution at 62.5 ± 2.5 ° C.

The substrate on which the light absorbing layer was formed was carried in the reaction solution for 10 minutes. The substrate was first washed with 5 wt% NH ₄ OH to form a buffer layer for a thin film solar cell with a thickness of 0.5 nm on the light absorption layer.

A ZnO light-transmitting electrode layer was formed on the buffer layer by metalorganic chemical vapor deposition (MOCVD) to produce a thin film solar cell.

Comparative Example 3

A soda lime glass substrate having a thickness of about 1 mm and having a Mo back electrode layer coated thereon was prepared. A CuGa target and an In target were sputtered on the substrate coated with the Mo back electrode layer, respectively, and heat-treated at 400 ° C for 20 minutes and at 550 ° C for 60 minutes under H ₂ Se and H ₂ S atmospheres, respectively, to obtain a composition of CuIn _0.7 Ga _0.3 SSe ₂ Was formed.

A buffer layer was formed on the light absorption layer using a chemical solution deposition method (Chemical Bath Deposition: CBD) as follows.

First, SC (NH ₂ ) ₂ solution was prepared by stirring DI water and 0.55M SC (NH ₂ ) ₂ at a temperature of about 82.5 ± 2.5 ° C. Separately, a mixed solution of NH ₄ OH and ZnSO ₄ .7H ₂ O was prepared by mixing 2.5M of NH ₄ OH and 0.1M of ZnSO ₄ .7H ₂ O at room temperature. The SC (NH ₂ ) ₂ solution and a mixed solution of NH ₄ OH and ZnSO _{4 ·} 7H ₂ O were charged into the reactor and mixed to prepare a reaction solution at 67.5 ± 2.5 ° C.

The substrate on which the light absorbing layer was formed was carried in the reaction solution for 10 minutes. The substrate was first washed with 5 wt% NH ₄ OH to form a buffer layer for a thin film solar cell with a thickness of 0.5 nm on the light absorption layer.

A ZnO light-transmitting electrode layer was formed on the buffer layer by metalorganic chemical vapor deposition (MOCVD) to produce a thin film solar cell.

Comparative Example 4

A soda lime glass substrate having a thickness of about 1 mm and having a Mo back electrode layer coated thereon was prepared. A CuGa target and an In target were sputtered on the substrate coated with the Mo back electrode layer, respectively, and heat-treated at 400 ° C for 20 minutes and at 550 ° C for 60 minutes under H ₂ Se and H ₂ S atmospheres, respectively, to obtain a composition of CuIn _0.7 Ga _0.3 SSe ₂ Was formed.

A buffer layer was formed on the light absorption layer using a chemical solution deposition method (Chemical Bath Deposition: CBD) as follows.

First, a solution of SC (NH ₂ ) ₂ was prepared by stirring DI water and 0.55M SC (NH ₂ ) ₂ at a temperature of about 87.5 ± 2.5 ° C. Separately, a mixed solution of NH ₄ OH and ZnSO ₄ .7H ₂ O was prepared by mixing 2.5M of NH ₄ OH and 0.1M of ZnSO ₄ .7H ₂ O at room temperature. The SC (NH ₂ ) ₂ solution and a mixed solution of NH ₄ OH and ZnSO _{4 ·} 7H ₂ O were put into the reactor and mixed to prepare a reaction solution at 72.5 ± 2.5 ° C.

The substrate on which the light absorbing layer was formed was carried in the reaction solution for 10 minutes. The substrate was first washed with 5 wt% NH ₄ OH to form a buffer layer for a thin film solar cell with a thickness of 0.5 nm on the light absorption layer.

A ZnO light-transmitting electrode layer was formed on the buffer layer by metalorganic chemical vapor deposition (MOCVD) to produce a thin film solar cell.

Evaluation Example 1: Evaluation of electrical characteristics

The reaction solutions used in the buffer layers of the thin film solar cells prepared in Examples 1 to 4 and Comparative Examples 1 to 4 were irradiated with light for 0 to 4 hours using a light transmittance measuring apparatus (UV Vis 3000, Hitachi) The change in transmittance was measured. The results are shown in Figure 4 and Table 1 below

division Light transmittance (%) Example 1 73.1 Example 2 68.1 Example 3 63.8 Example 4 59.3 Comparative Example 1 57.1 Comparative Example 2 45.0 Comparative Example 3 36.2 Comparative Example 4 4.1

4 and Table 1, the light transmittance of the reaction solution used in the buffer layer of the thin film solar cell fabricated in Examples 1 to 4 was higher than that of the reaction solution used in the buffer layer of the thin film solar cell prepared in Comparative Examples 1 to 4 Which is higher than the light transmittance.

Further, as shown in Example 2 and Comparative Example 1, the reaction used in the buffer layer of the thin film solar cell prepared in Example 2 in which the temperature of the reaction solution was lower than 70 ° C even though the concentration of the same ammonia compound, zinc source and sulfur source was included The light transmittance of the solution was about 11.0% higher than the light transmittance of the reaction solution used in the buffer layer of the thin film solar cell prepared in Comparative Example 1 in which the temperature of the reaction solution was 70 ° C or higher.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it is to be understood that the invention is not limited to the disclosed exemplary embodiments, but, on the contrary, It will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the present invention.

The present invention relates to a thin film solar cell, and more particularly, to a thin film solar cell comprising a substrate, a back electrode layer, a light absorbing layer, a buffer layer,

Claims (18)

Preparing a reaction solution having an ammonia compound, a zinc source, and a sulfur source at a temperature lower than 70 캜; And
Supporting a substrate on which a light absorbing layer is formed in the reaction solution,
Wherein the zinc source has a concentration of 0.01M to 0.09M. The method according to claim 1, wherein the preparing of the reaction solution is a step of preparing a reaction solution at 60 ° C to 70 ° C. The thin film solar cell according to claim 1, wherein preparing the reaction solution comprises separately preparing a solution containing the sulfur source and a mixed solution in which the ammonia compound and the zinc source are mixed, Lt; / RTI > 4. The method according to claim 3, wherein the step of preparing the sulfur source comprises the step of stirring the sulfur source in DI water at a temperature of 70 ° C to 90 ° C. 4. The method according to claim 3, wherein the step of preparing the mixed solution of the ammonia compound and the zinc source comprises mixing the ammonia compound and the zinc source at room temperature. The method according to claim 1, wherein the concentration of the ammonia compound is in the range of 1.0M to 5.0M. The method of claim 1, wherein the zinc source is _{ZnSO 4, ZnCl 2, Zn 2} (CH 3 COO), Zn (NO 3) 2, And a hydrate thereof. The method of manufacturing a thin film solar cell according to claim 1, The method according to claim 1, wherein the concentration of the zinc source is 0.01M to 0.07M. The method according to claim 1, wherein the oxysulfide is a thin film solar cell comprising a thiourea compound. The method according to claim 1, wherein the concentration of the sulfur source is 0.1M to 0.7M. The manufacturing method according to claim 1, wherein the manufacturing method further comprises cleaning after the step of supporting the substrate on which the light absorption layer is formed in the reaction solution. 12. The method according to claim 11, wherein the manufacturing method further comprises a step of drying after the cleaning step. The manufacturing method according to claim 12, wherein the drying step comprises a step of drying under an atmosphere of an inert gas. The method of claim 1, wherein the thin film solar cell is formed by forming a buffer layer of ZnS, ZnO, or ZnS (O, OH) on a substrate having the light absorption layer. 15. The method according to claim 14, wherein the buffer layer has a thickness of 10 nm to 50 nm. The method according to claim 1, wherein the reaction solution forms a thin film solar cell which is usable up to 6 hours. The method according to claim 1, wherein the light transmittance of the reaction solution is at least 60% from 4 hours after the reaction of the solution. Board;
A rear electrode layer formed on the substrate;
A light absorbing layer formed on the rear electrode layer;
A buffer layer formed on the light absorbing layer by the manufacturing method according to any one of claims 1 to 17; And
And a transparent electrode layer formed on the buffer layer.

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